如何在具有简单链表的函数中使用函数是 C

Question

我的练习是从 2 个文件中读取 2 个简单的链表：

F1:

1 2 3 4 5 6 7 8

F2:

6 7 8 9 10

然后列出共同的值，并列出2个结构的并集。这是到目前为止的代码：

#include <stdio.h>
#include <stdlib.h>

typedef struct node
{
 int key;
 struct node *next;

} NodeT, NodeT2, NodeTcom, NodeTuni;

NodeT *search(NodeT *head, int givenKey)
{
 //TODO: search the given key and return the first node containing it or NULL
 while (head != NULL)
 {
     if (head -> key == givenKey)
     {
         return head;
     }
     else
     {
         head = head->next;
     }
 }
 return NULL;
}

void print_list(NodeT *head)
{
 //TODO: print list keys
 if (head == NULL)
     printf("Empty list!");
 else
     while (head != NULL)
     {
         printf("%d ", head->key);
         head = head->next;
     }

 printf("\n");
}

void insert_last(NodeT **head, NodeT **tail, int givenKey)
{
 //TODO: insert the given key in the last position of the list given by head and tail;
 NodeT * p = (NodeT*)malloc(sizeof(NodeT));
 p->key = givenKey;
 p->next = NULL;
 if (*tail == NULL)
 {
     *head = *tail = p;
 }
 else
 {
     (*tail)->next = p;
     *tail = p;
 }
}

void uniune(NodeTuni **headU, NodeTuni **tailU, NodeT *head){

     while (head != NULL)
 {

     //printf("%d", head->key);
     insert_last(**headU, **tailU, head->key);

     head = head->next;
 }
}

int main()
{
 ///PRIMA LISTA
 NodeT *first = NULL;
 NodeT *last  = NULL;

 FILE *fp;

 fp = fopen("E:\F1.txt", "r");
 int temporary;
 while( fscanf(fp, "%d", &temporary) > 0)
 {
     insert_last(&first, &last, temporary);

 }
 fclose(fp);
 printf("Prima lista:");
 print_list(first);

 ///A DOUA LISTA
 NodeT2 *first2 = NULL;
 NodeT2 *last2  = NULL;

 FILE *fp2;
 fp2 = fopen("E:\F2.txt", "r");
 while( fscanf(fp2, "%d", &temporary) > 0)
 {
     insert_last(&first2, &last2, temporary);

 }
 fclose(fp2);
 printf("A doua lista:");
 print_list(first2);

 //PARTEA DE VERIFICARE DUBLU:
 ///LISTA UNITA
 NodeTuni *firstU = NULL;
 NodeTuni *lastU  = NULL;

 uniune(&firstU, &lastU, first);

 printf("Lista comuna:");
 print_list(firstU);




 return 0;
}

uniune 功能无效。我的问题是我不知道如何正确使用指针。感谢任何类型的帮助（可能使用具体代码）。

Answer 1

您不必 typedef 多种类型。它是无意义的并且只是令人困惑。
你不必使用 tail 只要你总是追加一个新节点到列表的最后位置。
类型最好选择*node，而不是**node
insert_last() 的参数。它与 return 下面提到的 insert_last() 的值。
相反 insert_last() 应该 return 指向创建列表的指针。然后你可以使递归变得容易。

那你试试看:

#include <stdio.h>
#include <stdlib.h>

#define FILE1 "E:\F1.txt"
#define FILE2 "E:\F2.txt"

typedef struct node {
    int key;
    struct node *next;

} node;

node *search(node *head, int givenKey)
{
    //TODO: search the given key and return the first node containing it or NULL
    while (head != NULL) {
        if (head->key == givenKey) {
            return head;
        } else {
            head = head->next;
        }
    }
    return NULL;
}

void print_list(node *head)
{
    //TODO: print list keys
    if (head == NULL) {
        printf("Empty list!\n");
        return;
    }

    while (head != NULL) {
        printf("%d ", head->key);
        head = head->next;
    }
    printf("\n");
}

node *insert_last(node *head, int givenKey)
{
    //TODO: insert the given key in the last position of the list given by head
    // return the first node

    if (head == NULL) {
        node *p = malloc(sizeof(node));
        if (p == NULL) return head;
        p->key = givenKey;
        p->next = NULL;
        return p;
    } else {
        head->next = insert_last(head->next, givenKey);
        return head;
    }
}

node *common(node *head1, node *head2)
{
    // create a new list of common values of head1 and head2
    // return the first node

    if (head1 == NULL || head2 == NULL) {
        printf("Empty list!\n");
        return NULL;
    }

    node *p = NULL;                             // create a new list
    while (head1 != NULL) {
        if (search(head2, head1->key)) {        // if found in both lists
            p = insert_last(p, head1->key);     // then append to the new list
        }
        head1 = head1->next;
    }
    return p;
}

node *uniune(node *head1, node *head2)
{
    // create a new list of union values of head1 and head2
    // return the first node

    node *p = NULL;                             // create a new list

    while (head1 != NULL) {
        if (! search(p, head1->key)) {          // copy new values of head1
            p = insert_last(p, head1->key);
        }
        head1 = head1->next;
    }

    while (head2 != NULL) {
        if (! search(p, head2->key)) {          // copy new values of head2
            p = insert_last(p, head2->key);
        }
        head2 = head2->next;
    }

    return p;
}

void free_list(node *head)
{
    // free the nodes of the list recursively
    if (head == NULL) return;
    free_list(head->next);
    free(head);
}

int main()
{
    ///PRIMA LISTA
    node *first1 = NULL;
    FILE *fp1 = fopen(FILE1, "r");
    if (fp1 == NULL) {
        fprintf(stderr, "cannot open %s\n", FILE1);
        exit(1);
    }
    int temporary;
    while (fscanf(fp1, "%d", &temporary) > 0) {
        first1 = insert_last(first1, temporary);
    }
    fclose(fp1);
    printf("Prima lista: ");
    print_list(first1);

    ///A DOUA LISTA
    node *first2 = NULL;
    FILE *fp2 = fopen(FILE2, "r");
    if (fp2 == NULL) {
        fprintf(stderr, "cannot open %s\n", FILE2);
        exit(1);
    }
    while (fscanf(fp2, "%d", &temporary) > 0) {
        first2 = insert_last(first2, temporary);
    }
    fclose(fp2);
    printf("A doua lista: ");
    print_list(first2);

    node *first3 = NULL;
    first3 = common(first1, first2);
    printf("Lista comuna: ");
    print_list(first3);

    node *first4 = NULL;
    first4 = uniune(first1, first2);
    printf("Lista unita: ");
    print_list(first4);

    free_list(first1);
    free_list(first2);
    free_list(first3);
    free_list(first4);

    return 0;
}

输出：

Prima lista: 1 2 3 4 5 6 7 8 
A doua lista: 6 7 8 9 10 
Lista comuna: 6 7 8 
Lista unita: 1 2 3 4 5 6 7 8 9 10

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